A bifunctional primitive strategy induces enhancements of large second harmonic generation and wide UV transmittance in rare-earth borates containing [B5O10] groups

Strong second-harmonic generation (SHG) and a short ultraviolet (UV) cutoff edge are two crucial yet often conflicting parameters that must be finely tuned in the exploration of nonlinear optical (NLO) materials. In this study, two new rare earth borate NLO crystals, K7BaSc2B15O30 (KBSBO) and Rb21Sr3.8Sc5.2B45O90 (RSSBO), were rationally designed through a bifunctional primitive strategy to achieve an optimized balance between favorable SHG efficiency and UV transparency. As anticipated, both KBSBO and RSSBO exhibit a wide UV transparency window below 190 nm. Notably, these tailored crystals display strong SHG responses, with RSSBO achieving a remarkable enhancement in SHG efficiency (2 × KDP), surpassing that of most deep-UV rare earth borates containing [B5O10] groups known to date. Theoretical calculations and structural analyses reveal that the impressive SHG activities primarily stem from the [B5O10] groups and [ScO6] polyhedra. These findings suggest promising potential for KBSBO and RSSBO crystals as beryllium-free deep UV NLO materials.

Recent Progress in Crystalline Borates with Edge-Sharing BO4 Tetrahedra

Crystalline borates have received great attention due to their various structures and wide applications. For a long time, the corner-sharing B-O unit is considered a basic rule in borate structural chemistry. The Dy₄B₆O₁₅ synthesized under high-pressure is the first oxoborate with edge-sharing [BO₄] tetrahedra, while the KZnB₃O₆ is the first ambient pressure borate with the edge-sharing [BO₄] tetrahedra. The edge-sharing connection modes greatly enrich the structural chemistry of borates and are expected to expand new applications in the future. In this review, we summarize the recent progress in crystalline borates with edge-sharing [BO₄] tetrahedra. We discuss the synthesis, fundamental building blocks, structural features, and possible applications of these edge-sharing borates. Finally, we also discuss the future perspectives in this field.

Discovery of SrZn2B6O12 with an unprecedented quadruple-layered configuration

A new borate, SrZn2B6O12, is found to show a quadruple-layered configuration. This rare quadruple-layer is stacked by two 2[Zn2B6O12]∞ double-layers that are constructed by two single-layers of 2[B4O7]∞ and 2[Zn2B2O4]∞.

Toward the Coordination Fingerprint of the Edge-Sharing BO4 Tetrahedra

The K₃Sb₄BO₁₃ (KSBO) material undergoes an uncommon symmetry increase upon cooling, from triclinic symmetry at room temperature to monoclinic symmetry at low temperature. The first-order phase transition is accompanied by shrinkage of the unit cell, resulting in the transformation of every pair of head-to-tail triangular BO₃ groups into one B₂O₆ unit featuring unique edge-sharing BO₄ tetrahedra. This is the first material with B₂O₆ units formed through temperature lowering and exhibiting a B-O anionic framework composed uniquely of isolated edge-sharing BO₄ tetrahedra. Several techniques including single-crystal X-ray diffraction experiments, Raman and ¹¹B magic-angle-spinning NMR spectroscopies, and, for the first time, B K-edge electron energy loss spectroscopy were used to evidence the rare and discrete B₂O₆ units. The complete transformation of BO₃ units into B₂O₆ units makes the KSBO compound the perfect candidate to extract information about B₂O₆ units whose signal can be unambiguously assigned.

Synthesis of the first nickel borate nitrate K7Ni[B18O24(OH)9](NO3)6· (H3BO3)

The novel potassium nickel borate nitrate K7Ni[B18O24(OH)9](NO3)6 ·(H3BO3) was obtained from a simple hydrothermal synthesis in a stainless-steel autoclave at T = 513 K starting with nickel dichloride hexahydrate, and boric and nitric acid with the pH adjusted to 8 by KOH. Single-crystal X-ray diffraction data provided the basis for the structure analysis and refinement. The compound crystallizes in the trigonal space group R3̅ (no. 148) with the lattice parameters a = 1222.29(8) and c = 5478.4(4) pm. Generally, K7Ni[B18O24(OH)9](NO3)6 ·(H3BO3) is comprised of nitrate layers and complex nickel borate layers surrounded by boric acid, nitrate anions, and potassium cations.

Four alkali metal molybdates with two types of Mo–O chains, ABMo3O10 (A = Li, B = Rb; A = Li, Na, K, B = Cs): synthesis, structure comparison and optical properties

The effects of cation size on the framework structures of four stoichiometrically equivalent alkali metal molybdates were discussed in detail.

Ni6B22O39·H2O – extending the field of nickel borates

Ni6B22O39·H2O was synthesized in a high-pressure/high-temperature reaction at 5 GPa/900°C. It crystallizes in the orthorhombic space group Pmn21 (no. 31) with the lattice parameters a=7.664(2), b=8.121(2) and c=17.402(2) Å. The crystal structure is discussed with regard to the isotypic compounds M 6B22O39·H2O (M=Fe, Co) and the structurally related phase Cd6B22O39·H2O. Furthermore, the characterization of Ni6B22O39·H2O via X-ray powder diffraction and vibrational spectroscopy is reported.

High-pressure synthesis and crystal structure of In3B5O12

Orthorhombic In3B5O12 was synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 12.2 GPa and 1500°C. Its structure is isotypic to the rare earth analogs RE 3B5O12 (RE=Sc, Er–Lu). In the field of indium borate chemistry, In3B5O12 is the third known ternary indium borate besides InBO3 and InB5O9. The crystal structure of In3B5O12 has been determined via single-crystal X-ray diffraction data collected at room temperature. It crystallizes in the orthorhombic space group Pmna with the lattice parameters a=12.570(2), b=4.5141(4), c=12.397(2) Å, and V=703.4(2) Å3. IR and Raman bands of In3B5O12 were theoretically determined and assigned to experimentally recorded spectra.

Ba2B10O17: a new centrosymmetric alkaline-earth metal borate with a deep-UV cut-off edge

Ba₂B₁₀O₁₇, a new barium borate, with a band-gap of 5.97 eV, possesses a wide transmission range from 180 to 3000 nm.

Two Cu-complex directed aluminoborates: from 2D layers to 3D frameworks

Two novel aluminoborates (1 and 2) containing Cu complexes have been prepared under solvothermal conditions. Both are built from AlO₄ groups and [B₅O_10−n(OH)_n] (n = 0 and 2) clusters. 1 features a 2D aluminoborate layer with 16-member rings, whereas 2 is a 3D framework stacked by different building layers, showing the first Cu-complex directed aluminoborate.